1. Field of the Invention
The present invention generally relates to an optic adaptor and more particular to an optic adaptor incorporating variable attenuator therein.
2. The Related Arts
Optic attenuators are often incorporated in optic communication network for selectively attenuating optic signal to match the requirement of particular systems. Optic attenuators are also used to attenuate optic signal for accessing system loss, simulation and tests.
A number of differently structured optic attenuators are available in the market. One commonly employed method for attenuating optic signal is to offset optic fibers with respect to each other which reduces signal coupling efficiency of the optic fiber and thus attenuating the optic signal passing therethrough. Another method that can be employed to attenuate optic signal is to separate opposing ends of two aligned optic fibers. The larger the distance between the opposing ends of the fiber is, the more attenuation can be achieved.
FIG. 1 of the attached drawings schematically shows the former method. An optic signal travels from a first optic fiber 81 to a second optic fiber 82. The optic fibers 81, 82 are offset a distance d with respect to each other. An example of this method is disclosed in U.S. Pat. No. 5,263,106.
FIG. 2 of the attached drawings schematically shows the later method. An optic signal travels from a first optic fiber 91 to a second optic fiber 92. Ends of the fibers 91, 92 are separated a distance S. The attenuation loss Ls of the optic signal is dependent upon the distance S, as shown in FIG. 3 of the attached drawings. A separation distance of 2.5 mm may cause a loss of 26 dB.
The later method requires only mechanically moving the optic fibers with respect to each in order to adjust attenuation. Thus it can be easily incorporated with an optic adaptor to joint two fibers in line.
FIG. 4 is an example of the later method shown in U.S. Pat. No. 4,666,243 which comprises a guide sleeve 3 for receiving and aligning two optic fibers 1, 2. Two end sleeves 4, 5 are respectively threaded to fibers 1, 2. The end sleeves 4, 5 are threadingly connected to each other for adjusting a distance d between the fibers 1, 2. The end sleeves 4, 5 are secured in position by a nut 6. A disadvantage of the conventional optic adaptor is that the end sleeves 4, 5 are rotated with respect to each other in adjusting the distance d. The rotation of the end sleeves may cause the optic fibers 1, 2 to move or rotate with respect to each other and thus leading to damage to the optic fibers 1, 2. Further, it may not be possible to realize continuous adjustment of the device.
It is thus desirable to provide an optic device for overcoming the above problems.
Accordingly, an object of the present invention is to provide an optic adaptor incorporating signal attenuator.
Another object of the present invention is to provide an optic adaptor with variable signal attenuation wherein optic fibers are not allowed to rotated with respect to each other in order to reduce the likelihood of damage to the optic fibers.
A further object of the present invention is to provide an optic adaptor incorporating continuous adjustment of attenuation.
To achieve the above objects, in accordance with the present invention, an optic adaptor connects first and second optic fibers in an aligned but spaced fashion for attenuation of optic signals traveling between the optic fibers. The adaptor comprises a base secured to a patch panel and connected to the first optic fiber. The base defines a bore receiving and retaining a first end of a sleeve that receives the first optic fiber. A cylinder has a proximal end axially and movably received in the bore to receive a second end of the sleeve. A fiber connection member is mounted to the cylinder and attaches the second optic fiber to the cylinder with the second optic fiber received in the second end of the sleeve. A knob ring threadingly engages the cylinder. The knob is rotatably mounted to but is not axially movable with respect the base body whereby rotation of the knob induces axial movement of the cylinder and the second optic fiber with respect to the base body and the first optic fiber. Thus the distance between the optic fibers can be changed.